The present invention relates to a method for de-oiling crankcase ventilation gases and apparatus for accomplishing the method.
The method and the associated apparatus are known from practical experience resulting from a plurality of application cases. The known separating elements for de-oiling crankcase ventilation gases, in most cases cyclones, comprise two decisive operation values namely the separating efficiency and the differential pressure depending on the volume stream of the streaming crankcase ventilation gases, the so called Blow-By-Gases. Depending on the operation a volume stream area will result wherein the separating efficiency and also the differential pressure of the separating element are optimally adjusted to the requirements of the internal combustion engine.
Therein the volume stream of the crankcase ventilation gases is dependent on operating values like load condition and numbers of revolution of the associated internal combustion engine, and the wear condition thereof. When operating an internal combustion engine such a large volume stream area will result from these values that disadvantageously it cannot be covered with one separating element because the optimal operating condition of the separating element is only met in a very small area. In other areas the separating efficiency, e.g., with small volume streams, will decrease below a required level, or with a correspondingly larger volume stream the resulting differential pressure will exceed a tolerable value.
Therefore, it is the object of the invention to provide a method and associated apparatus for de-oiling crankcase ventilation gases which will operate under all operating conditions of the internal combustion engine in an optimal area.
The method according to the invention is characterized in that the volume stream of the crankcase ventilation gases is divided in at least two partial volume streams, and at least one partial volume stream is guided through at least one oil separating element, wherein the magnitude of the at least two partial volume streams is controlled depending on the magnitude of the volume stream. Therein advantageously is attained that by a corresponding control with small volume streams only one separating element is used, and that with large volume streams the at least two separating elements are used. Of course it is possible to use three or four or even more separating elements each of them being controlled such that the fed partial volume stream is optimally cleaned from oil droplets.
The advantages are that the separating efficiency and the differential pressure are always kept in the optimal area, and this is accomplished even under extreme operating conditions like push operation and/or extreme wear of the internal combustion engine.
Several apparatus for accomplishing the method according to the invention are stated wherein in a first embodiment at least two oil separating elements arranged in parallel are present with a common control element arranged upstream which divides the volume stream of the crankcase ventilation gases depending on the magnitude thereof in at least two partial volume streams and guides these streams to the at least two oil separating elements. The advantage of this solution is the relatively simple construction with only one control element.
An alternate embodiment provides that at least two oil separating elements are provided arranged in parallel with each having a control element which depending on the magnitude of the fed partial stream, controls the downstream arranged oil separating elements, i.e., opens, or closes, or partly opens. In this embodiment a control element is necessary for each oil separating element which because of the smaller partial stream volume to be received mostly is smaller compared with the first embodiment.
It is advantageous that in the last embodiment an additional common control element is arranged upstream of the other control elements which additional control element divides the volume stream of the crankcase ventilation gases depending on the magnitude thereof in correspondingly many partial volume streams. Therein the common control element is connected to the downstream arranged several control elements in a suitable mariner, e.g., by electrical control signal lines such that control commands from the common control elements may be transferred to the downstream arranged control elements, and in particular control signals for opening or closing may be transferred.
In a further alternative it is provided that at least two oil separating elements are provided arranged in parallel, each of them having a partial stream flowing therethrough wherein the magnitude thereof may be controlled by a control element associated with an oil separating element with the control element being arranged in parallel with the oil separating element regarding the flow direction. In this arrangement the number of the control elements is equal to the number of oil separating element however, these oil separating elements do not have the full partial streams flowing therethrough, whereby in many cases a smaller construction is possible.
Furthermore, a further alternative is provided wherein at least two oil separating elements are provided arranged in series with each a control element arranged upstream, wherein each control element, depending on the fed volume streams, divides this stream in two partial streams with the one thereof flowing to the control element in front of the downstream arranged oil separating element, and wherein the other partial stream flows through a by-pass line which passes by the downstream arranged oil separating element. In the latter embodiment, a too large volume stream may be passed by the oil separating elements if this is tolerable in certain operating conditions, or is required.
In all preceding embodiments of the apparatus, in a first simple embodiment, the control element may be a passive element which may be actuated directly by the volume stream or by a force exerted by this stream. In this manner on the one hand a simple and inexpensive construction is attained, and on the other hand a high reliability during operation is attained.
Alternately, the control element may be an active element that, depending on a control signal, may be actuated with the control signal resulting from a measurement of the volume stream. This embodiment requires a somewhat higher technical effort, however, enables a more accurate control and a stronger influence, e.g., on the course of control characteristics.
Regarding the measurement of the volume streams mentioned above, a first further development of the apparatus provides that a measuring device for measuring the volume streams encompasses a hot wire having an electrical current flowing therethrough, and that the control element may be actuated electrically. As an advantage, the measurement of the volume stream and the actuation of the control element is attained electrically such that a simple transfer of measuring signals in control signals may be possible purely electrically.
An alternate embodiment provides that a measuring device for measuring the volume stream encompasses a venturi pressure sensor, and that the control element may be actuated mechanically, preferably by a diaphragm acting on a tappet of this control element. This embodiment has the advantage that the measurement and also the actuation of the control element may be attained purely mechanically such that a transfer of mechanical measuring values in electrical signals or vice versa from electrical signals to mechanical control values is not necessary.
In order to keep the apparatus compact and simple and easy to mount, preferably it is provided that the control element is arranged directly in the gas inlet of the associated oil separating element, and that by means of the control element, the inlet cross-section of the oil separating element may be varied, preferably continuously or in several steps between an open and a closed position.
An alternate embodiment of the apparatus which has the same effect, provides that the control element is arranged directly in the gas outlet of the associated oil separating element, and that by means of the control element the gas outlet cross-section of the oil separating element may be varied, preferably continuously or in several steps, between an open and a closed position.
In order to avoid, in the embodiment of the apparatus described last, that with a closed gas outlet cleaned gas escapes through the oil outlet of the oil separating element in a non-required fashion, it is furthermore provided that in addition to the control element directly in the oil outlet of the associated oil separating element, an additional control element is arranged, that by means of the additional control element the oil outlet cross-section of the oil separating element may be varied, preferably continuously or in several steps between an open and a closed position, and that the control element and the additional control element are coupled with each other, and may be commonly adjusted. This coupling of the control element and the additional control element ensures that the oil outlet is open only with an open gas outlet, and that with a closed gas outlet also the oil outlet is closed.
In a concrete embodiment of the coupled unit of control element and additional control element, it is proposed that the control element and the additional control element each comprise a valve ball biased in closing direction by weight or spring force, wherein the valve ball of the control element has a larger diameter than the valve ball of the additional control element, and wherein the two valve balls are connected with each other by a coupling element for common adjustment. Hereby a common and identical movement of the valve balls, and thereby a coupled adjustment of control element and additional control element, is guaranteed. In its simplest embodiment the coupling element is a thin and light rod connecting the two valve balls with the rod forming an asymmetrical dumbbell with the two valve balls.